Paper machine belt

ABSTRACT

The invention relates to a paper machine belt, some of the threads or all of the threads being made partially or entirely of a bioplastic.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

This application is related to utility model number 20 2012 103 846.3,filed Oct. 8, 2012, in the Federal Republic of Germany, the entiredisclosure of which is incorporated herein and to which priority isclaimed.

FIELD OF THE INVENTION

The invention relates to a paper machine belt.

BACKGROUND OF THE INVENTION

Paper machine belts are endless textile products or textile productsmade endless by a seam with a large length and a large width, of whichthe structure and the chosen material is adapted to the specificrequirements of a paper machine. The paper machine belts circulate inthe paper machine and thereby supporting the sheet of paper being formedas it passes through the paper machine, thereby enabling both the paperformation and drying processes. A distinction can be made here betweenthree basic types of paper machine belt according to their application.

In the first part of the paper machine—the forming part—single ormulti-layered fabrics are used on to which the paper pulp is applied sothat a strip of paper is formed. Water is removed from the latterthrough the forming fabric by the effect of gravity and by the effect ofnegative pressure applied by means of suction boxes. Forming fabricsmust therefore on the one hand be highly permeable and on the other handhave good fibre retention on their outside. In the subsequent section ofthe paper machine—the press part—the strip of paper is transferred ontopress felts and passed through roller presses, any liquid stillcontained within the strip of paper is pressed out by the roller nippressure and subsequently pushed through the press felt. Press feltsbasically comprise a support in the form of a thread system onto whichone or a number of fibre layers are needled. The thread system can be awoven or knitted fabric or a nonwoven scrim. Combinations of thesethread systems are also known. The press part is followed by the dryingpart in which the strip of paper is passed onto dryer fabrics which helpto guide the strip of paper over hot rollers. Water is removed bythermal means. Dryer fabrics are generally made of an open woven fabricor of a spiral linked belt (with regard to the genus: EP 0 171 891 A1,EP 0 472 072 A1 and EP 0 763 623 B1). As well as these, there are alsoother forms of paper machine belts, for example so-called shoe pressbelts which are produced from a support, consisting e.g. of a wovenfabric or a nonwoven scrim and an impermeable polymer layer applied tothe latter.

In the past, the thread systems of such paper machine belts wereproduced from wool or cotton. However, the mechanical properties of thelatter were so restricted that they were not able to keep up with thedevelopments being made in paper machine technology. For a number ofdecades, therefore, paper machine belts have been produced exclusivelyfrom plastics based on fossil raw materials such as polyethylene,polypropylene, polyimide, polyester, polyethylene terephthalate,polyether ether ketone and the like. The amount of such plasticsconsumed here is considerable due to the unfavourable environmentalconditions in the paper machine. In addition, paper machine belts have aservice life of only a few months and must be replaced frequently by newbelts.

The fossil raw materials used in the production of polymeric plastics,in particular the petrochemical raw materials such as mineral oil, arebecoming less abundant. Since there is still no replacement for mineraloil used in the production of fuels, there is a general need to save theexisting mineral oil as far as possible and to keep it for theapplications for which it is still indispensable.

SUMMARY OF THE INVENTION

The object underlying the invention is to provide alternative materialsfor the production of paper machine belts which are able to replace theplastics based on petrochemical raw materials used currently tomanufacture paper machine belts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

According to the invention this object is achieved by the paper machinebelt being made partially or entirely from a bioplastic, in particularbioplastics which are produced using one or more renewable rawmaterials, especially plant raw materials. By using such plastics acontribution is made to saving the fossil based resources. Moreover, thedisposal of bioplastics is less problematic and their material can to alarge extent be salvaged for reuse.

Both biologically non-degradable and biologically degradable bioplasticscan be used in order to achieve the object in question. In the lattercase, however, degradation should only occur after the paper machinebelt has become inoperative so that the paper machine belt retains itsinitial properties until the end of its service life. Biologicaldegradation should only be possible some time after this.

The following biopolymers in particular are suitable for use in papermachine clothing. Bioplastics which are based on starch, in particularthermoplastic starch, can be used. The raw material for starch can bemaize, wheat, potato or tapioca. A water-resistant starch plastic can beused here, as given in the examples from EP 0 596 437 A2, WO 02/051284A2 or WO 96/19599 A1.

A further raw material is cellulose that is further processed, forexample, by means of esterification. Examples of cellulose polymers aregiven in JP 2009-138022 A1, JP 2003-082160 A1, WO 2011/097700 A1, JP2004-010844, JP 2004-131670 A1, JP 2003-335898 A1 and CN 101 492 837 A1.

Further appropriate bioplastics are polylactic acid (PLA), as describedfor example in WO 02/051284 A2 and in WO 2011/097700 A1 for the purposeof the production of fibres and textile threads, but also in JP2003-082160 A1, JP 2008-223177A1 and JP 2008-297680 A1. Also suitable ispolytrimethylene terephthalate (PTT) based on 1,3-propanediol (PDO), asgiven in the examples from WO 2010/078328 A2, US 2010/0168372 A1, JP2008-223177 A1 and JP 2008-297680 A1.

Also suitable as a bioplastic is bio-based polyamide (PA), as describedfor example in JP 2010-222721 A1, WO 2011/094673 A2, WO 2011/066619 A1or WO 2011/066620 A1. The same applies to polyhydroxyalkanoate (PHA), asdisclosed e.g. in JP 2008-223177 A1 and JP 2008-297680, and to bio-basedpolyethylene (PE).

Other suitable biopolymers are polyvinyl chloride (PVC) made ofbio-based ethene or ethyne, bio-based polybutylene terephthalate (PBT),mentioned e.g. in US 2010/0168371 A1 and WO 2010/078328 A2,polyphenylene sulfide (PPS), polyethylene terephthalate (PET), describede.g. in WO 2010/101698 A2, CN 101525416 A1, WO 2010/078328 A2, US2010/0168371 A1 and WO 2009/120457 A2, polyethylene-co-isosorbideterephthalate polymer (PEIT), polyester based on 1,3-propane diol,mentioned e.g. in US 2010/0168371 A1, WO 2010/078328 A2 and WO2008/088501 A1, and polyurethane (PUR), that is based on bio-basedpolyols and bio-based isocyanates.

The full content of the previously cited prior art documents is includedin the content of the present description, and are incorporated hereinby reference in their entirety. This applies in particular to theproduction processes described in the publications and also to thecombinations respectively with other materials and raw materials. Itgoes without saying that the previously specified bioplastics and rawmaterials—also with one another or as required—can—as far as possible—bemixed with the known mineral oil-based plastics such as to form e.g.compounds or blends.

If the paper machine belt has a thread system with threads or is made ofthe latter, some of the threads or all of the threads should be madepartially or entirely of the bioplastic. This thread system can be inthe form of a woven or knitted fabric or a non-woven layer of threads,or also of a spiral link band and be formed from combinations of thelatter. In the thread system there can be threads which are in the formof monofilaments—also wires—and/or of multifilaments or twisted yarns.Both fibres made of bioplastics and fibres made of mineral oil-basedplastics can be used as multifilaments.

The thread system can also have a number of layers, at least one layercontaining threads or consisting of threads which are partially orentirely made of a bioplastic. Here too combinations of bioplastic andpetrochemical plastics are possible, for example by the one layer beingproduced from a bioplastic and the other layer being produced from apetrochemical plastic, or both layers from a combination of both typesof plastic. If the environmental conditions in the paper machine allowit, both layers should be produced from a respective bioplastic suitablefor this purpose so as to be able to dispense as far as possible withpetrochemical plastics.

As in known paper machine belts, one layer of the thread system can bein the form of a woven or knitted fabric and a further layer a non-wovenlayer in which the threads are laid one over the other and are not wovenor knitted together.

As already mentioned, there can be threads within the thread systemwhich are partially made of the bioplastic and partially of apetrochemical plastic, both plastics being mixed as a compound or blendand/or some of the threads being produced from bioplastic and othersbeing produced from petrochemical plastic. This can for example takeplace in a form such that the threads are in the form of core/sheaththreads and that the core is produced from the bioplastic and the jacketis produced from the petrochemical plastic or vice versa. However, theremay also be threads which are in the form of multifilament threadsand/or twisted yarns, some of the filaments possibly being made of thebioplastic and some of the filaments being made of the petrochemicalplastic.

In particular, the paper machine belt can be in the form of a formingfabric that is to be used in the forming section to form the strip ofpaper. Here the threads, which are made partially or entirely of thebioplastic, should have properties within the following ranges:

-   thread diameter: 0.08-0.5 mm;-   tensile force: 2-110 N;-   thread extension upon breakage: 10-32%;-   thread elasticity modulus: 80-9250 N/mm².

In a further configuration of the invention provision is made such thatthe paper machine belt is provided with a coating and the coating ismade partially or entirely of a bioplastic, for example one of thebioplastics identified in more detail above. Independently of this, thepaper machine belt can also be provided with a fibre layer, the fibrelayer being made partially or entirely of a bioplastic.

The paper machine belt described above can preferably be in the form ofa forming fabric, a press felt or a dryer fabric.

In an embodiment of the invention, the paper machine belt as describedherein is installed in any or all of the forming part, press part anddrying part of the paper making machine. Those skilled in the art willunderstand that separate belts are installed in each of these parts. Thepaper machine belt is supported by and moves along and on typicallydriven rollers for thereby moving the paper web as it is being formedfrom one part of the paper making machine to the next successive part.The paper machine belts as herein described will be adapted for the partof the machine in which the belt is to be located. The belt in each partthus has different specifications and requirements as compared with thebelts in the other parts of the paper making machine.

It will be apparent to one of ordinary skill in the art that variousmodifications and variations can be made in construction orconfiguration of the present invention without departing from the scopeor spirit of the invention. Thus, it is intended that the presentinvention cover all such modifications and variations, and as may beapplied to the central features set forth above.

1. A paper machine belt, characterised in that some of the threads orall of the threads are made partially or entirely of a bioplastic. 2.The paper machine belt according to claim 1, characterised in that thebioplastic is produced using one or more renewable raw materials, inparticular plant raw materials.
 3. The paper machine belt according toclaim 1, characterised in that the bioplastic is not biologicallydegradable.
 4. The paper machine belt according to claim 1,characterised in that the bioplastic is created such that it does notdegrade or only degrades biologically after the paper machine belt hasbecome inoperative under the environmental conditions in a papermachine.
 5. The paper machine belt according to claim 1, characterisedin that the bioplastic or its raw material is chosen from a group thatconsists of starch, cellulose polymer, polylactic acid (PLA),polytrimethylene terephthalate (PTT) made of bio-based 1,3-propanediol(PDO), bio-based polyamide (PA), polyhydroxyalkanoate (PHA), bio-basedpolyethylene (PE), polyvinyl chloride (PVC) made of bio-based ethene orethyne, bio-based polybutylene terephthalate (PBT), bio-basedpolyphenylene sulfide (PPS), bio-based polyethylene terephthalate (PET),bio-based polyethylene-co-isosorbide terephthalate polymer (PEIT),polyurethane (PUR) made of bio-based polyol and/or bio-based isocyanate.6. The paper machine belt according to claim 1, characterised in thatthe paper machine belt has a thread system with threads or is made ofthe latter, some of the threads or all of the threads being madepartially or entirely of a bioplastic.
 7. The paper machine beltaccording to claim 6, characterised in that the thread system forms oneor more woven or knitted fabrics or non-woven yarn layers orcombinations of the latter and/or a spiral link band.
 8. The papermachine belt according to claim 6, characterised in that there arethreads in the thread system which are in the form of monofilamentsand/or multifilaments.
 9. The paper machine belt according to claim 6,characterised in that the thread system has a number of layers and thatat least one layer contains threads or consists of threads which aremade partially or entirely of a bioplastic.
 10. The paper machine beltaccording to claim 6, characterised in that the thread system has anumber of layers and that at least one layer contains threads which aremade partially or entirely of a petrochemical plastic.
 11. The papermachine belt according to claim 9, characterised in that one layer ofthe thread system is in the form of a woven fabric and a further layeris in the form of a non-woven layer.
 12. The paper machine beltaccording to claim 6, characterised in that there are threads within thethread system which are partially made of the bioplastic and partiallyof a petrochemical plastic.
 13. The paper machine belt according toclaim 12, characterised in that the threads are in the form ofcore/sheath threads and that the core is made of the bioplastic and thecore of the petrochemical plastic or vice versa.
 14. The paper machinebelt according to claim 12, characterised in that there are threads inthe thread system which are in the form of multifilament threads oryarns, some of the filaments being made of the bioplastic and some ofthe filaments being made of the petrochemical plastic.
 15. The papermachine belt according to claim 6, characterised in that the papermachine belt is in the form of a forming fabric and the threads whichare made partially or entirely of the bioplastic have properties withinthe following ranges: thread diameter: 0.08-0.5 mm; tensile force: 2-110N; thread extension upon breakage: 10-32%; thread elasticity modulus:80-9250 N/mm².
 16. The paper machine belt according to claim 1,characterised in that the paper machine belt is provided with a coatingand the coating is made partially or entirely of a bioplastic.
 17. Thepaper machine belt according to claim 1, characterised in that the papermachine belt is provided with a fibre layer and the fibre layer is madepartially or entirely of a bioplastic.
 18. The paper machine beltaccording to claim 2, characterised in that the bioplastic is notbiologically degradable.
 19. The paper machine belt according to claim2, characterised in that the bioplastic is created such that it does notdegrade or only degrades biologically after the paper machine belt hasbecome inoperative under the environmental conditions in a papermachine.
 20. The paper machine belt according to claim 3, characterisedin that the bioplastic is created such that it does not degrade or onlydegrades biologically after the paper machine belt has becomeinoperative under the environmental conditions in a paper machine.
 21. Apaper making machine, comprising: a forming part, a press part and adrying part, each of the parts having positioned and movable therein apaper machine belt, at least one of the paper machine belts ismanufactured from a bioplastic selected from the group consisting ofstarch, cellulose polymer, polylactic acid (PLA), polytrimethyleneterephthalate (PTT) made of bio-based 1,3-propanediol (PDO), bio-basedpolyamide (PA), polyhydroxyalkanoate (PHA), bio-based polyethylene (PE),polyvinyl chloride (PVC) made of bio-based ethene or ethyne, bio-basedpolybutylene terephthalate (PBT), bio-based polyphenylene sulfide (PPS),bio-based polyethylene terephthalate (PET), bio-basedpolyethylene-co-isosorbide terephthalate polymer (PEIT), polyurethane(PUR) made of bio-based polyol and/or bio-based isocyanate.